1. Field of the Invention
The present invention relates generally to refrigeration, and in a more particular sense has reference to those structures in the refrigeration category described commercially as refrigerated display cases. Such cases are of the type used in food markets, and within this general category the invention comes within the field of invention wherein the display case has an air passage through which air is circulated about the displayed food products, often flowing as an air curtain across an open front of the display case. In yet a more particular sense, the invention has reference to improvements in this type of display case, wherein a service opening is provided at the rear of the case, through which dairy product support carts may be rolled into and out of the case. The invention relates to a hollow structure normally closing the service opening through which the carts are moved, the structure being both a part of the air flue or conduit, and a foldable door for the service opening.
2. Description of the Prior Art
It has heretofore been proposed to provide, in refrigerated display cases of the type generally described above, service openings at the rear of the display cases, through which dairy product support carts can be rolled into and out of the case. It has been proposed that the carts be left within the case to provide convenient means for displaying the products without the necessity of unloading the same and transferring them to shelves such as are normally provided in refrigerated display cases.
It has further been suggested to provide, for the service openings of the cases, closures that serve as air passages communicating with other portions of the air conduit above and below the closures when the closure are in their normal, closed positions.
Usually, closures of this type when used in refrigerated display cases are of the sliding or hinged type. Such doors, unfortunately, present certain problems with respect to rolling carts into and out of the display case.
To appreciate the problems that have arisen, it should first be noted that cases of this type are often of great length, particularly when used in large supermarkets. In such installations, it is common to provide an array of identical display cases, end-to-end, that may extend to an overall length of perhaps 60 to 70 feet, typically.
In such installations, it is desirable that the maximum amount of the total, overall length be available for stocking the displayed food products, that is to say, there should be minimum spacing between the dairy carts, since open spaces between side-by-side carts represent completely wasted, refrigerated areas in the product display space of the display case. Additionally, such open spaces are visually unattractive and detract from the merchandising capability of the case as a means for promoting sales of the displayed products.
Typically, a dairy product support cart, of the type that is rolled into and out of the case to serve as shelving accessible to the customer, is approximately 36" in width. It follows that if the service opening is closed by a series of hinged doors, there would normally be one door for each cart location. That door would have to be of a width that would have a transverse dimension sufficiently greater than the cart width to permit clearance on both sides of the cart when it is moved through the service opening defined by opening of the door. Further, between adjacent doors mullions must be provided if the doors are hinged, of sufficient width and strength to support the doors when they are swung to open positions.
If follows that in such arrangements, substantial open spaces occur between adjacent carts when the carts are in position within the display cases.
The disadvantages of using hinged doors, whether or not they also provide air ducts when in their closed positions, can thus be readily noted when their use is contemplated for dairy cases into which product support carts are to be loaded.
The same problems arise with respect to sliding closures. Whether or not these are hollowly formed to define air ducts in their closed positions, they share with hinged doors the problem that they of necessity leave open spaces between adjacent carts within the display case, a highly undesirable feature which, as noted above, not only detracts from the merchandising ability of the equipment, but also reduces its overall, effective length as a product display area.
It has in fact been proposed to provide foldable flexible closures for the rear surface openings of display cases of the type described, as shown in U.S. Pat. No. 4,034,572, issued July 12, 1977 to the assignee of the present application. While to some extent these facilitate the positioning of carts directly side-by-side with minimum open areas between them, they at the same time take away from the available duct space at the rear of the case. It is desirable, in this connection, that the duct be continuous from end-to-end of the case, so as to provide for uniform refrigeration and an efficient air curtain across the front access opening of the display case.